A non-prism total station is currently used for various surveys. By using the total station, an observation point located even at a high place can easily and precisely be measured without disposing a temporary scaffold.
The non-prism total station utilizes a reflected light of a laser beam emitted therefrom toward the observation point. However, for example, no reflected light is available from the corner or corner portion of the building, so that accurate coordinates of the corner cannot be obtained. Therefore, conventionally, a substitute observation point is provided on a wall surface in the vicinity of the corner, and the coordinates of the observation point are specified as the coordinates of the corner. However, the coordinates of the substitute observation point are not the actual coordinates specifying the coordinates of the corner.
In the meantime, there are instances where it is required to specify a flat surface by using a non-prism total station. For example, showing a distribution of cracks generated in a wall surface of the building by means of three-dimensional coordinate data needs data specifying the wall. Unfortunately, the actual wall surface is not completely flat and may include unevenness due to aging degradation. Therefore, for example, the specified surface, i.e., an equation of surface, specified by the coordinate data of three observed points on the wall surface may not reproduce the actual wall surface.
Patent Document 1: JP 2004-333211 A
Patent Document 2: JP 2010-85311 A